In North America there are a wide variety of forest tree species. Many of these tree species make excellent durable building materials, while other tree species quickly decay or are prone to be riddled by insects. It has been found that a variety of tree species endure because they comprise natural preservatives that repel insects and discourage decay. Included in this grouping of naturally insect and decay resistant varieties of trees are cypress, cedar, chestnut, and live-oak trees. However, as the demand for housing has grown, the supply of these trees has proven to be insufficient to keep pace with the demand for durable products that are manufactured from the trees.
One approach to increasing the supply of structural wood products is to use younger tree stocks to make engineered wood products. Engineered wood products or “EWP,” also referred to as “structural composite lumber” or “SCL,” are fiber-glue composites made by various processes. EWP products are different from panel type products such as plywood, oriented strand board (OSB), particle board, and the like. EWP products can be manufactured to any length, offering an advantage over normal wood members which are limited in length by the size of available raw wood. Systems and methods for manufacturing engineered wood products are described in U.S. patent application Ser. No. 11/162,747 (U.S. Patent Application Publication No. 2006/0086427) entitled “A System and Method for the Manufacture of Reconsolidated or Reconstituted Wood Products,” and U.S. patent application Ser. No. 11/162,748 (U.S. Patent Application Publication No. 2006/0060290) entitled “Systems and Methods for the Production of Steam-Pressed Long Fiber Reconsolidated Wood Products,” the disclosures of which are incorporated herein by reference and made a part hereof.
As described in the referenced and incorporated patent applications, the process of making engineered wood products initially involves crushing and scrimming of small logs into long strands or scrim. After drying and adding adhesives and/or bonding agents to the wood strands or scrim, the wood strands or scrim are reconstituted into billets, and then the billets are formed into beams and other engineered wood products by using steam press technology in which steam and/or pressure are utilized to produce high quality engineered wood products. Although engineered wood products are often made from scrim, those skilled in the art will understand that such products can also be made from strands, veneers, fibers, and combinations thereof.
In response to the limited supply of naturally insect and decay resistant trees for the production of lumber products and the use of less resistant tree stock for making EWP, modern builders have developed processes to add man-made preservatives to lumber products that are produced from non-insect and decay resistant tree species in order to produce large amounts of durable commodity building products needed today. Presently, there are processes that use pressure to introduce chemical preservatives into the structure of wood or a wood product. The wood or wood product to be treated is initially inundated in preservative chemicals, and thereafter placed into a pressure vessel and pressurized in order to force chemical preservatives into the wood structure and thus become a barrier against insects and decay. Common chemicals that are used in today's processes include water-borne chromated copper arsenate (CCA), ammoniacal copper zinc arsenate (ACZA), and ammoniacal copper quat (ACQ).
The conventional methods that are used to chemically treat wood and wood products have limitations and drawbacks such as high costs in preserving a wood product, uneven distribution of biocides throughout the wood product, and the need for biocides that are not safe to use in habitable spaces or for framing around them. Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies, especially in connection with the manufacture of engineered wood products.